The primary objective of this study is to determine A) whether HU enhances long term viral suppression in subjects receiving IDV, ddI and d4T, B) whether switching from IDV, ZDV (or d4T), and 3TC to IDV, ddI, and d4T enhances long-term viral suppression and C) whether switching from IDV, ZDV (or d4T) and 3TC to IDV, d4T, ddI and HU enhances long-term viral suppression. The secondary objectives are to determine the CD4 cell counts and percentages in the three regimens; to evaluate the safety and tolerance of HU in the study population; to evaluate the effects of HU on the decay rate of latently infected cells; to correlate the relationship between adherence to the treatment regimen and virologic outcome; and to characterize drug resistance in subjects with virologic failure.